Method and Apparatus for Collecting Solar Energy

ABSTRACT

Various embodiments for an improved solar collector are disclosed. For example, a heat absorber can be positioned inside an evacuated chamber formed by a frame and a transparent cover. Heat absorbed by the heat absorber within the evacuated chamber can be delivered to a heat transfer fluid inside a chamber of a heat exchanger. The heat exchanger chamber can also reside in the evacuated chamber. In a preferred embodiment, the heat absorber comprises a planar heat pipe. Also in a preferred embodiment, a reflector can be positioned to reflect energy radiated by the heat absorber back to the heat absorber.

BACKGROUND AND SUMMARY OF THE DISCLOSURE

The present invention is directed toward an improved solar collectordesign. Extensive work has been done in the field of solar collectors.Examples of solar collectors that are known in the art include flatplate solar collectors and evacuated tube solar collectors.

An issue faced by designers of solar collectors is how undesired heatloss to the outside environment can be reduced. That is, heat capturedby the solar collector can be lost to the outside environment throughprocesses known as convection, conduction and radiation. Such heat lossreduces the efficiency and output of a solar collector. Another issuefaced by designers of solar collectors is how a solar collector can bedesigned to increase the percentage of its exposed surface area that isused to absorb heat.

The inventors disclose a number of solar collector embodiments that theinventors believe address and improve on one or more of these issues.

In accordance with a first aspect of an exemplary embodiment of theinvention, disclosed herein is an apparatus for collecting solar energy,the apparatus comprising (1) a planar heat pipe configured to absorbheat, (2) a frame surrounding the planar heat pipe, the frame forming achamber within which at least a portion of the heat pipe resides, and(3) a transparent cover engaged with the frame to enclose the chamber,and wherein the chamber comprises an evacuated chamber.

Also disclosed herein is a method for collecting solar energy, themethod comprising absorbing heat with a solar collector, the solarcollector comprising a planar heat pipe positioned inside an evacuatedchamber formed by a frame and a transparent cover.

Further disclosed herein is an apparatus for collecting solar energy,the apparatus comprising (1) a planar heat pipe configured to absorbheat, the heat pipe having a plurality of holes, (2) a frame, the framecomprising a bottom member and a plurality of sidewalls forming achamber within which the heat pipe resides, (3) a transparent coverengaged with the frame to enclose and seal the chamber, wherein thechamber comprises an evacuated chamber, (4) a heat exchanger incooperation with the heat pipe, the heat exchanger comprising a heatexchanger chamber and an output, the heat exchanger being configured toreceive and transfer the heat absorbed by the heat pipe to the output,wherein the heat exchanger chamber is positioned inside the evacuatedchamber, and (5) a plurality of free-floating pins positioned to supportthe heat pipe without the heat pipe contacting the frame, the pinshaving a bottom portion for engaging the bottom member and a top portionfor engaging the transparent cover, and wherein the pins pass throughthe heat pipe holes.

In accordance with another aspect of an exemplary embodiment of theinvention, disclosed herein is an apparatus for collecting solar energy,the apparatus comprising: (1) a heat absorber configured to absorb heat,(2) a frame adapted to form a chamber within which at least a portion ofthe heat absorber resides, (3) a transparent cover engaged with theframe to enclose the chamber, the cover configured to permit solarenergy to enter the chamber and impact the heat absorber, and (4) areflector positioned and configured to reflect energy radiated by theheat absorber back to the heat absorber.

Further disclosed is a method comprising, within a solar collectorhaving a heat absorber positioned inside a chamber, reflecting energyradiated by the heat absorber back to the heat absorber with areflector.

Also disclosed is a method comprising, within a solar collector having aheat absorber positioned inside a chamber, the chamber being formed by abottom member, a plurality of side walls and a transparent cover,positioning an energy reflector between the heat absorber and the bottommember.

Further still, disclosed herein is an apparatus comprising a flat platesolar collector having an evacuated chamber within which a heat absorberand a reflector are positioned, the reflector being positioned beneaththe heat absorber for reflecting energy radiated by the heat absorberback to the heat absorber.

In accordance with another aspect of an exemplary embodiment of theinvention, disclosed herein is an apparatus for collecting solar energy,the apparatus comprising (1) a heat absorber configured to absorb heat,(2) a frame surrounding the heat absorber, the frame forming a chamberwithin which the heat absorber resides, (3) a transparent cover engagedwith the frame to enclose and seal the chamber, wherein the chambercomprises an evacuated chamber, and (4) a heat exchanger in cooperationwith the heat absorber, the heat exchanger comprising a heat exchangerchamber and an output, the heat exchanger being configured to receiveand transfer the heat absorbed by the heat absorber to the output,wherein the heat exchanger chamber is positioned inside the evacuatedchamber.

Furthermore, disclosed herein is a method for collecting solar energy,the method comprising (1) absorbing heat with a heat absorber, whereinthe heat absorber is positioned inside an evacuated chamber formed by aframe and a transparent cover of a solar collector, and (2) transferringthe absorbed heat to a heat exchanger, the heat exchanger comprising aheat exchanger chamber, wherein the heat exchanger chamber is alsopositioned inside the evacuated chamber.

In accordance with yet another aspect of an exemplary embodiment of theinvention, disclosed herein is an apparatus for collecting solar energy,the apparatus comprising (1) a heat absorber configured to absorb heat,the heat absorber comprising a plurality of holes, (2) a frame, theframe comprising a bottom member and a plurality of sidewalls that forma chamber within which the heat absorber resides, (3) a transparentcover engaged with the frame to enclose and seal the chamber, whereinthe chamber comprises an evacuated chamber, and (4) a plurality offree-floating pins positioned to support the heat absorber without theheat absorber contacting the frame, the pins having a bottom portion forengaging the bottom member and a top portion for engaging thetransparent cover, and wherein the pins pass through the heat absorberholes.

Also disclosed is a method for collecting solar energy, the methodcomprising (1) absorbing heat with a heat absorber wherein the heatabsorber is positioned inside an evacuated chamber formed by a frame anda transparent cover of a solar collector, the heat absorber comprising aplurality of holes, and (2) supporting the heat absorber within theframe with a plurality of free-floating pins that pass through the heatabsorber holes, the pins positioned to support the heat absorber withoutthe heat absorber contacting the frame, the pins having a bottom portionfor engaging a bottom member of the frame and a top portion for engagingthe transparent cover.

In accordance with still another aspect of an exemplary embodiment ofthe invention, disclosed herein is an apparatus for collecting solarenergy, the apparatus comprising: (1) a vacuum pump line for connectionto a vacuum pump, (2) a plurality of branch vacuum pump lines forconnection to the vacuum pump line, (3) a plurality of solar collectorsconnected to at least one of the branch vacuum pump lines to form anarray of solar collectors, each solar collector comprising an evacuatedchamber, a heat absorber positioned at least partially inside thechamber, and a tube valve for connection to the at least one branchvacuum pump line, and (4) a solenoid valve connecting the vacuum pumpline with the at least one branch vacuum pump line, the solenoid valvebeing configured to open and close to maintain a vacuum pressure insidethe chambers of the solar collectors in the array and isolate the solarcollectors in the array from the vacuum pump line in response to acontrol signal.

Further disclosed is a method for collecting solar energy, the methodcomprising: (1) collecting energy with a plurality of solar collectors,each solar collector comprising an evacuated chamber and a heat absorberpositioned inside the evacuated chamber, and (2) using at least onesolenoid valve to maintain a vacuum pressure inside the evacuatedchambers and isolated the evacuated chambers from an upstream vacuumpressure fault.

In accordance with still another aspect of an exemplary embodiment ofthe invention, disclosed herein is an apparatus for collecting solarenergy, the apparatus comprising (1) a plurality of branch pipe lines,(2) a trunk pipe line configured to deliver heat transfer fluid to theplurality of branch pipe lines, and (3) a plurality of solar collectorsserially connected to at least one of the branch pipe lines to form anarray of solar collectors.

Moreover, disclosed herein is a method comprising (1) delivering heattransfer fluid from a trunk pipe line to a plurality of branch pipelines, wherein at least one of the branch pipe lines comprises aplurality of solar collectors serially connected to form an array ofsolar collectors, and (2) collecting energy with the array of solarcollectors to heat the delivered heat transfer fluid.

These and other features and advantages of various embodiments of thepresent invention will be apparent to those having ordinary skill in theart upon review of the specification and drawings contained herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a)-(c) depict an exemplary solar collector in accordance withan embodiment of the invention;

FIG. 2( a) depicts an exemplary solar collector in accordance withanother embodiment of the invention;

FIG. 2( b) depicts an exemplary reflector that can be used in the solarcollector embodiment of FIG. 2( a);

FIG. 2( c) depicts an exemplary solar collector in accordance with yetanother embodiment of the invention;

FIGS. 2( d) and (e) depict exemplary transparent covers for use withexemplary solar collector embodiments;

FIGS. 3( a)-(f) depict an exemplary solar collector in accordance withyet another embodiment of the invention;

FIG. 4 is an exploded cross-sectional view of the solar collectorportion around the manifold heat exchanger from FIG. 3( a);

FIG. 5 depicts various views of an exemplary planar heat pipe that canbe used with the solar collectors disclosed herein;

FIGS. 6( a)-(d) depict various heat pipe embodiments showing how aplurality of cylindrical heat pipes can be arranged to approximate aplanar heat pipe;

FIG. 7 depicts a cross-sectional view of an exemplary planar heat pipehaving an upper surface with a plurality of ridges and troughs;

FIGS. 8( a)-(e) depict various views of exemplary planar heat pipes withpatterned surfaces;

FIGS. 9( a) and (b) depict exemplary embodiments for a manifold heatexchanger;

FIGS. 10( a)-(c) depict additional exemplary embodiments for a manifoldheat exchanger having different inlet/outlet port arrangements;

FIG. 11( a) is a cross-sectional view of an exemplary manifold heatexchanger that illustrates how a heat transfer fluid is heated;

FIGS. 11( b)-(d) depict examples of how heat transfer fluid can flowthrough a dual-chamber bidirectional manifold heat exchanger embodiment;

FIGS. 12( a)-(d) depict exemplary support pins that can be used invarious solar collector embodiments;

FIGS. 13( a)-(c) depict exemplary arrays that can be created from aplurality of the solar collectors disclosed herein;

FIG. 13( d) depicts an exemplary technique for ganging solar collectorstogether in an array;

FIG. 14 depicts an exemplary arrangement of solar collector arrays on asupport member providing tilting elevation for the solar collectors;

FIGS. 15( a) and (b) depict exemplary vacuum systems that can beemployed by exemplary solar collector arrays

FIG. 16 depicts a top view of an exemplary solar collector in accordancewith another embodiment;

FIGS. 17( a) and (b) depict an exemplary embodiment of a solar collectorthat is encased in insulation; and

FIGS. 18( a) and (b) depict exemplary solar collectors having aplurality of heat pipes sharing a single evacuated chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1( a) depicts a cross-sectional view of an exemplary solarcollector 100 in accordance with an embodiment of the invention. FIG. 1(b) depicts a top view of this solar collector 100, and FIG. 1( c)depicts a perspective view of this solar collector 100. Solar collector100 comprises a heat absorber 102, preferably a planar heat pipe asdiscussed below, positioned inside a chamber 108 formed by a box frame104 and a transparent cover 106. However, it should be understood thatthe heat absorber 102 need not be a heat pipe as other types of heatabsorbers could be used. For example, the heat absorber 102 can be amanifold heat absorber where a heat transfer fluid flowing throughpiping absorbs heat and this heated heat transfer fluid is then passedout of the solar collector through a heat exchanger port 114. However,the inventors believe that the use of a heat pipe as the heat absorber102 can provide some advantages relative to such a manifold designbecause the heat pipe permits the solar collector system to exhibit ahigher flow rate for the heat transfer fluid at lower pressure in thepiping.

Box frame 104 comprises a bottom member 120 and a plurality of sidewalls122 formed to create a box having an open chamber 108. A transparentcover 106 that is adapted to pass energy such as light from the outsideenvironment into chamber 108 is positioned atop the box frame 104 toenclose chamber 108.

Box frame can be formed from a material that is sufficiently strong tosupport the weight of the transparent cover, and with embodiments wherethe interior chamber of the box frame is evacuated the material shouldalso be capable of adequately maintaining a vacuum. Examples of boxframe materials include aluminum, copper and plastic. Also, box framepreferably has a rectangular shape with a long dimension and a shortdimension as shown in FIGS. 1( a)-(c), particularly in the top view ofFIG. 1( b). However, this need not be the case. For example, a squarebox frame could be used. Further still, shapes of other polygons such ashexagons could also be used if desired by a practitioner. However, arectangular shape is preferred because it is expected that a rectangularshape will be more amenable to field assembly and mass production. Itshould also be understood that the dimensions of the box frame 104 canbe varied based on the desires of a practitioner in view of thestructural strength needs. An exemplary length (the long dimension shownin FIG. 1( b)) and width (the short dimension shown in FIG. 1( b)) forthe box frame can be 4 feet by 8 feet but other dimensions could readilybe accommodated. An exemplary height (the vertical dimension shown inFIG. 1( a)) for the box frame can be around 3-6 inches. However, onceagain, other heights can be used. Furthermore, while the exemplary boxframe 104 is described as comprising a bottom member 120 and a pluralityof sidewalls 122, it should be understood that the box frames 104 can beformed from not only discrete bottom member units and sidewall units butthe box frame 104 can also be formed from an integral structure having abottom member and a plurality of sidewalls.

The transparent cover 106 is preferably a pane of glass or othermaterial that transmits electromagnetic energy for impacting the heatabsorber 102. For example, as is understood in the window arts, thetransparent cover 106 can be formed from a material that efficientlypasses a desired spectrum range of energy radiated by the sun. This paneis preferably sized to effectively match the length and width dimensionsof the box frame 104 and enclose the chamber 108. The thickness of thetransparent cover 106 can be varied as desired by a practitioner so longas the transparent cover is sufficiently strong to withstand externalforces and pressures imposed by select weather events and the like whenthe solar collector 100 is in use (e.g., storms, hail, strong winds,etc. depending on the expected weather patterns in the geographiclocations where the solar collector would be deployed). The thicknessfor the transparent cover 106 can vary as desired by a practitionerbased on a number of factors. The transparent cover thickness mustbalance competing factors such as being able to pass a sufficient amountof energy (it is expected that increasing thickness would reduce thepercentage of energy impacting the outer surface of the cover 106 thatis passed to the chamber 108) while also being sufficiently strong tomaintain its integrity when the chamber 108 is under vacuum pressure (itis expected that increasing thickness would increase the cover'sstrength). Another variable that could impact the cover's thickness ishow many support pins 112 are used. Generally speaking, the use of moresupport pins 112 rather than fewer would better support the cover 106and permit a less thick cover 106. However, each support pin 112 alsotakes away from the surface area of the heat absorber that is used toabsorb energy, in which case a practitioner will need to balance thesefactors when selecting a number of support pins 112 and cover thickness.Exemplary thicknesses for the transparent cover 106 can be ¼, ½ or ⅜ ofan inch.

Any of a number of techniques can be used to securely engage thetransparent cover 106 with the top of box frame 104 to enclose thechamber 108. For example, a sealant material can be applied around theperimeter of the top of the box frame 104, and the transparent cover 106can be securely attached to the box frame 104 via this sealant. Overtime, the box frame 104 and cover 106 will adhere to the sealant to forma secure gasket-type engagement between the frame 104 and cover 106. Toaccelerate this process, the cover 106 can be seal set duringfabrication by applying the sealant and cover 106 to the box frame 104and evacuating the chamber 108. The pressure created by the vacuum willforce the cover 106 against the sealant and accelerate this adheringprocess. Exemplary sealants that can be used include silicon, Teflon orother heat-resistant materials with sufficient give and adheringproperties. The sealant can be applied around the rim of the box frame104 as a tape. Also, a practitioner may choose to apply one or morespring clips 300 to the transparent cover 106 and box frame sidewalls122 to further secure the transparent cover 106 to the box frame 104(see, for example, FIGS. 3( a) and 4 discussed below). Such spring clips300 can further secure the cover 106 in place, especially while thesolar collector 100 is being transported to the location where it is tobe used. If desired, for embodiments where the solar collector's chamber108 is an evacuated chamber, the inventors believe that the spring clips300 could be removed after the solar collector is put in place in thefield because it is believed that the vacuum pressure in the chamberwill be sufficient for keeping the cover 106 engaged against the frame104.

Furthermore, it should be understood that the sealant need not possessadhesive properties described above; in embodiments wherein the chamber108 is evacuated, the sealant need only serve to create a seal to helpmaintain the vacuum pressure of the chamber 108. For example, the vacuumpressure and/or spring clips 300 could be used to secure the cover 106to the frame 104 in the absence of an adhesion of the seal to the cover106 and frame 104.

A heat absorber 102 is positioned inside the chamber 108. As explainedbelow, the heat absorber 102 is preferably a planar heat pipe. As energysuch as sunlight enters the chamber 108 through transparent cover 106and impacts the upper surface 116 of the heat absorber 102, the heatabsorber absorbs this energy and transfers heat created by the absorbedenergy to a portion of the heat absorber in communication with amanifold heat exchanger 110. The manifold heat exchanger 110 has aplurality of ports 114, and receives a heat transfer fluid into achamber via an intake port 114 a. This heat transfer fluid, which servesas a carrier fluid, is heated by a portion of the heat absorber 102 thatresides within or contacts the heat exchanger chamber. Heated heattransfer fluid then exits the manifold heat exchanger 110 via an outtakeport 114 b. This heated heat transfer fluid can then be delivered todownstream appliances as needed to provide desired energy. For example,the heated heat transfer fluid can be delivered to a chiller unit or thelike to help power an air conditioning operation. Any of a variety ofknown heat transfer fluids can be used by the heat exchanger 110, andthe selection of an appropriate heat transfer fluid can made by a personof ordinary skill in the art based on factors such as the expectedoperating temperatures of the system. For example, water (or a mix ofwater and antifreeze) can be used in a system where the expectedtemperature range does not exceed around 212 degrees Fahrenheit. Athigher temperatures, other heat transfer fluids known in the art couldbe employed.

Also, while the examples of FIGS. 1( a)-(c) show the heat exchanger 110having male ports 114, it should be understood that the heat exchanger110 could also be configured with female ports 114. Such female ports114 would then engage with piping to receive heat transfer fluid andoutput heated heat transfer fluid. Any of variety of known techniquescould be used for engaging piping with the ports 114, whether male orfemale. For example, the ports 114 could have threading that permitspiping to be screwed on, O-ring-type connections could be made betweenthe ports 114 and piping, or any of a variety of other techniques.

Preferably, chamber 108 is evacuated after the transparent cover 106 isput in place atop the box frame 104. Furthermore, it is preferred thatthis evacuation occur in the field after the solar collector has beenpositioned on site where it is to be used. By maintaining a vacuuminside chamber 108, the solar collector will be better insulated fromconvection heat loss to the ambient environment. That is, the vacuuminside chamber 108 will help reduce the rate at which heat captured bythe heat absorber escapes to the environment by convection.

To evacuate the chamber a tube valve 124 can be installed at somelocation along the box frame. This valve 124 permits the solarcollector's chamber 108 to be connected to a pump line for creating acontinuous vacuum pressure inside the chamber. This tube valve 124 canbe a conventional access valve with a tube extension as is known in theheating and cooling arts. The pump line to which this valve 124 isconnectable would be connected to a vacuum pump and the vacuum pumpwould maintain the vacuum pressure inside the chamber. As explainedbelow, in embodiments where the solar collector 100 is deployed in anarray of solar collectors, a pump line can serve multiple solarcollectors if desired.

To further improve the insulation properties of the solar collector 100,the chamber portion of the manifold heat exchanger 110 is alsopreferably positioned inside the evacuated chamber 108, as shown inFIGS. 1( a)-(c) (see also chamber 900 in FIG. 4). With such anembodiment, the heat loss due to convection from the heat exchanger 110can be reduced. Furthermore, the amount of piping external to theinsulation provided by the vacuum through which the heated heat transferfluid flows is reduced.

Moreover, the heat absorber 102 is preferably positioned inside thechamber 108 such that the heat absorber chamber does not directlycontact the box frame's bottom member 120 or sidewalls 122. As shown inFIG. 4, a standoff sleeve 412 that serves as a conductive barrier toheat can be used as at least part of the heat exchanger's ports 114 tosupport that heat exchanger's reservoir chamber away from the frame 104.By avoiding such contact, the solar collector reduces heat loss from theheat absorber to the outside environment via conduction. Preferably,there is a gap of around ¼ to 1 inch between the heat absorber 102 andthe sidewalls 122 and a similar gap between the heat absorber 102 canthe bottom member 120, as shown in FIG. 1( b). However, it should beunderstood that other gap dimensions could be used with a caveat that itis generally preferred to not use too large of a gap between the heatabsorber 102 and the sidewalls 122 so as to maximize the exposed surfacearea of the heat absorber 102 that captures sunlight.

To support the heat absorber 102 in a manner that avoids direct contactwith the box frame's bottom member 120 and sidewalls 122, a plurality ofsupport pins 112 are used. Preferably, these support pins 112 are“free-floating” within the chamber 108 of the box frame 104. What ismeant by “free-floating” is that the support pins 112 are not attachedto the box frame 104. Essentially, if one were to remove the transparentcover 106 and heat absorber 102 and turn the box frame 104 upside down,the pins would fall out. The inventors believe that by usingfree-floating pins rather than pins that are fixedly attached to theframe 104 (or cover 106), the solar collector will better be able toaccommodate the thermal expansions and contractions that can be expectedto occur as a result of heating and cooling, particularly when oneconsiders that different materials used in the solar collector willlikely have different thermal expansion/contraction properties. Theinventors also believe that the use of free-floating support pins mayreduce thermal losses due to convection. Furthermore, for exemplaryembodiments, the support pins 112 also provide support to thetransparent cover 106, particularly when under pressure from a vacuum inchamber 108. The heat absorber 102 is preferably configured with aplurality of holes through which the pins 112 are passed as shown inFIGS. 1( a) and (b) to support the heat absorber 102 and transparentcover 106. While the holes shown in FIGS. 1( a)-(c) are generallycircular in shape, it should be understood that the holes may be formedby gaps of any shape if desired by a practitioner. A practitioner canalso select a desired spacing of holes and pins along the heat absorber102 so as to adequately support the cover 106. As noted above, factorssuch as the thickness of the cover 106 and the expected weatherconditions where the solar collector is to be deployed all factor intohow many pins 112 are needed and how they should be spaced.

An exemplary embodiment of a free-floating support pin 112 is shown ingreater detail in FIGS. 12( a) and (b). In this embodiment, the supportpin 112 is generally cylindrical, and it has a bottom portion 1200 of afirst diameter and an upper portion 1202 of a second diameter, whereinthe first diameter is larger than the second diameter. This creates ashoulder portion 1204 upon which the heat absorber 102 rests, as shownin FIG. 1( a). An upper face 1206 of the upper portion 1202 engages andprovides support to the transparent cover 106. A bottom face 1208 of thebottom portion 1200 engages the bottom member 120 of the box frame 104.As a free-floating support pin, neither upper face 1206 nor bottom face1208 is attached to the transparent cover 106 or bottom member 120.

It should be noted that while the exemplary embodiment of FIGS. 12( a)and (b) is shown to have a generally cylindrical shape, other shapescould be used for the support pins 112, such as square shapes,rectangular shapes, or other polygonal shapes.

To reduce conduction losses to the outside environment via a path fromthe heat absorber 102 through the pins 112 to the box frame 104, thepins are preferably made out of material that is a poor conductor ofheat, such as a ceramic. However, it should be understood that othermaterials could be used if desired by a practitioner. For example,ceramic end caps could be placed over metal support pins.

Furthermore, as shown in FIG. 12( c), a cushion layer 1220 could beattached to the upper face 1206 of the support pins to providecushioning between the pins 112 and cover 106 for accommodating thermalexpansion/contraction and/or the vacuum pressure. This cushion layer canbe formed of a silicon material or the like. A similar cushion layer1222 could be applied to the bottom face 1208 of the support pins (seeFIG. 12( d)). Moreover, both the upper and bottom faces 1206 and 1208can employ such cushion layers 1220 and 1222 if desired.

FIG. 2( a) is a cross-sectional view of another exemplary solarcollector embodiment. The solar collector 100 of FIG. 2( a) is similarto the solar collector shown in FIGS. 1( a)-(c), except the solarcollector 100 of FIG. 2( a) includes a reflector 200 positioned betweenthe bottom surface 118 of the heat absorber 102 and the bottom member120 of the box frame 104. The reflector 200 is thus positioned toreflect energy radiated by the heat absorber 102 back to the heatabsorber 102. In this way, radiation losses from the solar collector tothe outside environment can be reduced. The reflector 200 is preferablyof a planar shape and sized to cover the bottom surface area of thechamber 108.

FIG. 2( b) is a side view of an exemplary reflector 200. The reflector200 is basically a mirror or other polished surface having a substrate202, wherein a reflective coating layer 204 sits atop the substrate 202.The substrate 202 is preferably a flat planar pane of glass. However, asnoted above, any suitably polished surface could be used. The coating204 is preferably a coating that is configured to reflect energy of aselect wavelength corresponding to the energy that is expected to beradiated by the heat absorber 102. For example, the coating 204 can be acoating that reflects infrared (IR) energy. However, it should beunderstood that other coatings that are energy-reflective could be used.The selection of a particular coating can be made based on the desiresof a practitioner using knowledge about reflective coatings prevalent inthe window and glass industry.

It is worth noting that, with a preferred embodiment, the reflector 200need not be configured to reflect visible light as the reflector 200 isnot likely to receive much if any direct visible light because the heatabsorber is positioned to block substantially all sunlight from reachingthe reflector 200. In fact, with some embodiments, the reflector 200 maynot reflect visible light at all and would appear black ornon-reflective to an observer unlike the conventional mirrors that havebeen used with conventional solar collectors. Thus, contrary to pastsolar collector designs which have used mirrors to concentrate visiblelight onto a desired location, the solar collector embodiment of FIG. 2(a) uses a reflector 200 to reflect energy radiated by the heat absorber102 back to the heat absorber 102.

Furthermore, if desired, a practitioner can also place a reflector 200around the internal face of the sidewalls 122 within chamber 108 tominimize heat loss through the sidewalls. Alternatively, the internalface of the sidewalls 122 can themselves serve as the reflector byhighly polishing the sidewall's internal faces to provide better energyreflective properties. Similarly, the bottom member 120 could serve asthe reflector itself through such polishing. Further still, thesidewalls and/or bottom member (whether polished or not) can be coveredwith energy reflective coating 204 to serve as the reflector. Furtherstill, such a coating 204 can be applied directly to the bottom member120 to serve as the reflector.

Moreover, if desired, a practitioner could also place an energyreflective coating 222 on the underside of the transparent cover 106, asshown in FIG. 2( d). This energy reflective coating 222 would bepositioned to reflect energy radiated upward from the heat absorber 102back to the heat absorber. Furthermore, because the cover 106 needs totransmit electromagnetic energy such as sunlight from above into thechamber 108, this energy reflective coating 222 is preferably a one-wayenergy reflective coating 222, as known in the window and glassindustry, that permits energy to pass in one direction but reflectsenergy in the other direction. Moreover, to further improve theperformance of cover 106, an anti-reflective treatment 224 may be placedon the upper surface of the cover 106 if desired by a practitioner toimprove the way the cover 106 captures energy for transmission throughto chamber 108 (see FIG. 2( e)). Such a treatment 224, which may takethe form of a coating, secondary cover (e.g., a Fresnel lens) or thelike would better capture low angle sunlight that strikes the cover 106and provide the low angle sunlight energy to the chamber 108.

FIGS. 3( a)-(f) are views of another exemplary solar collectorembodiment. FIG. 3( a) is a cross-sectional view of an exemplary solarcollector 100 along the long dimension of the solar collector. FIG. 3(c) is a cross-sectional view of the solar collector 100 of FIG. 3( a)along the short dimension of the solar collector. With this embodiment,a plurality of spring clips 300 are used for securing the transparentcover 106 to the box frame. The inventors believe that these clips wouldhelp secure the cover 106 to the frame 104, particularly duringtransportation of a solar collector. If desired, the clips 300 can berun more or less continuously along the length and width of the solarcollector. However, a spacing of spring clips 300 with longer intervalscould be used. Also, the front and side sidewalls 122 include a ledge302 that enhanced the structural strength of these sidewalls 122.Preferably, the heat absorber 102 does not contact the ledges 302, asshown in FIGS. 3( a) and (c).

FIG. 4 illustrates an exploded view of the rear section of FIG. 3( a).In this figure, the spring clip 300 used to secure the transparent cover106 to the box frame 104 can be seen in greater detail. Furthermore,FIG. 4 shows that the sidewalls 122 can include a portion 404 that formsan internal ledge around the inner perimeter of the sidewalls near thetransparent cover 106. This internal ledge portion 404 can providesupport for the transparent cover 106. The sidewalls 122 can alsoinclude a portion 406 extending vertically above the ledge to laterallyprotect the transparent cover 106 and restrict undesired lateralmovement of the transparent cover 106. Further still, this portion 406may extend laterally outward relative to lower portions of the sidewalls122 to form a surface 408 upon which a portion of the spring clip 300can grip to secure the spring clip 300 in place. However, it should alsobe understood that this upper portion can be recessed relative to thelower part of the sidewall 122 (together with a notch in the sidewallupper portion for receiving the spring clip 300) so that multiple solarcollectors can be more flushly engaged against each other in an array ifdesired by a practitioner. Furthermore, the transparent cover 106 mayinclude a sealant layer 402 extending around its perimeter to form aseal with the frame 104 as explained above. The sealant layer 402 maycover around ½ to ¾ of an inch of the cover's edge portions. Also, thissealant layer may be formed from silicon or other suitable materials.Spring clip 300 can also engage the exposed surface of the sealant layer402 to secure the transparent cover 106 in place.

In the example of FIG. 4, it can also be seen that the bottom of the boxframe 104 has been configured with an open path area 430 enclosed by thelateral and rear sidewalls 122, an upper portion 410 and an internalwall 414 (see also FIG. 3( f)). Upper portion 410 can be a plateextending inward into the solar collector interior and perpendicularlyfrom the rear sidewall 122, as shown in FIG. 4. The upper portion 410may include holes through which the heat exchanger ports 114 pass and ahole through which a valve stem 124 for creating a vacuum within thechamber 108 passes. Piping (not shown) for delivering heat transferfluid to and taking heat transfer fluid away from the heat exchanger 110can pass through the open path area 430. The piping can pass into theopen path area 430 through a hole 310 in the lateral sidewalls 122, asshown in the side view along the long dimension of the solar collectorin FIG. 3( b). The heat exchanger ports 114 may include a standoffsleeve 412 as shown in FIG. 4 to engage against the upper portion 410 ofthe path area 412. This standoff sleeve 412 both supports the heatexchanger's reservoir chamber 900 away from the frame 104 to reducepotential conduction losses and serves as a conductive barrier to heatwith respect to a potential heat flow from the heat exchanger reservoirchamber 900 to the frame 104 and for any piping that connects with theheat exchanger 110. For example, the sleeve 412 through which any pipingthat connects to the heat exchanger's ports 114 passes, and would thusserve as a barrier to heat conduction between the piping and frame 104.To provide this barrier to heat conduction, the sleeve 412 is preferablyformed of a material that is a poor conductor of heat such as a ceramicmaterial. The standoff sleeve 412 may fit through a hole in the upperportion plate 410 and include a flange rim 420 as shown in FIG. 4 forsecuring the sleeve 412 to the upper portion plate 410. Bolts throughthe flange rim 420 and plate 410 can secure the standoff sleeve 412 inplace.

Also, the internal wall 414 is preferably positioned laterally inwardrelative to the outer internal edge of the upper portion 410, as shownin FIG. 4. This creates a ledge 416 extending laterally inward into thesolar collector interior from the internal wall 414. The reflector 200engages the bottom surface of this ledge 416. A sealant layer 450 can beused to providing sealing action between the reflector 200 and ledge416. Further still, another sealant layer 452 can provide sealing actionbetween the reflector 200 and frame bottom member 120, as shown in FIG.4. These sealant layers 450 and 452 can also be formed of a siliconmaterial or the like. A support material 460 (e.g., backerboard of thelike) can be positioned below the bottom member 120 if desired tofurther support the collector 100.

FIG. 3( d) shows a side view of the solar collector 100 of FIGS. 3(a)-(c) along a short dimension of the solar collector. FIG. 3( e) is atop view of the solar collector 100 of FIGS. 3( a)-(d). As can be seen,the heat absorber 102 takes up the vast majority of the solarcollector's exposed surface area. FIG. 3( f) is a bottom view of thesolar collector 100 of FIGS. 3( a)-(e). For example, the inventorsbelieve that around 95%-98% of the solar collector's surface area cantaken up by the heat absorber 102 to collect energy.

FIG. 5 shows a preferred embodiment for the heat absorber 102. As notedabove, in a preferred embodiment, the heat absorber is a planar heatpipe 500. The central frame of FIG. 5 shows a top view of an exemplaryplanar heat pipe 500. The planar heat pipe 500 can be largelysymmetrical with respect to its top and bottom, so this central framecan also depict a bottom view of the planar heat pipe 500. However, thisneed not be the case. Furthermore, as noted below, different treatmentscan be applied to the upper and bottom surfaces 116 and 118 to enhanceits performance. The upper frame of FIG. 5 shows a cross-sectional viewof the planar heat pipe 500 along its long dimension. The left frame ofFIG. 5 shows a cross-sectional view of the planar heat pipe 500 alongits short dimension. As is known in the art, a “heat pipe” is a closedstructure, typically with an internal vacuum, that efficiently transfersheat from a first location to a second location. A planar heat piperefers to a heat pipe that has a generally planar shape in that it isgenerally flat and exhibits a length and width that are much larger thanits thickness. An exemplary thickness for the planar heat pipe 500 canbe around ½ to 1 inch. An exemplary length and width for the planar heatpipe 500 can be similar to the length and width for the frame's chamber108 such that the heat pipe 500 fits inside the frame's chamber 108 savefor a gap around the chamber perimeter and sufficient space is left inthe chamber for accommodating portions of the heat exchanger not takenup by the heat pipe. However, it should be understood that otherlengths, widths and thicknesses could be used. The planar heat pipe 500preferably has a plurality of holes 502 through which the support pins112 can pass. The spacing for these holes 502 can be chosen as desiredby a practitioner to balance the need for adequately supporting the heatpipe 500 and transparent cover 106 against the desire to maximize theheat absorbing surface area of the planar heat pipe 500.

The planar heat pipe 500 preferably includes a portion 902 (see FIGS. 4and 9( a)-(b)) that is to be located inside the heat exchanger 110 fordelivering heat to the heat transfer fluid inside the heat exchanger110. Thus, the planar heat pipe 500 is preferably configured to deliverheat absorbed by exposed surfaces of the heat pipe to portion 902 insidethe heat exchanger 110 to heat the heat transfer fluid.

The heat pipe's upper and bottom surfaces 116 and 118 can be sheets of aheat absorbent material (e.g., copper, aluminum, titanium, etc.). As isunderstood in the heat pipe art, these sheets can be brought together attheir ends leaving a chamber between them that is subjected to a vacuumpressure. Furthermore, a coating can be applied to the outer surfaces ofthe heat pipe to enhance the heat pipe's heat absorption and heatrejection properties. A coating on the upper surface 116 of the heatpipe can enhance heat absorption and heat rejection, while a coating onthe bottom surface 118 can serve to reflect heat that would otherwise beradiated out the bottom surface 118 back into the heat pipe. Theinventors note that an appropriate heat pipe 500 can be built by a heatpipe manufacturer according to the desired parameters of a practitionersuch as the thickness of the heat pipe walls (e.g., the thickness of thecopper sheets or the like), the expected operating temperature for theheat pipe, the coatings that are desired for the heat pipe's outersurfaces, the amount of vacuum pressure expected within chamber 108, thedesign/shape of the heat exchanger 110 and the expected angle of use(e.g., whether the heat pipe is expected to be positioned in aneffectively flat orientation or a more tilted orientation).

While the exemplary planar heat pipe 500 of FIG. 5 is shown to have aflat surface, it should be understood that the surface of the planarheat pipe need not be entirely flat. For example, as shown in FIGS. 6(a)-(d), a plurality of cylindrical heat pipes 600 can be arrangedtogether to approximate a planar heat pipe 500. FIG. 6( a) is aperspective view of a plurality of cylindrical heat pipes arranged toapproximate a planar heat pipe. FIG. 6( b) is a cross-sectional view ofsuch a planar heat pipe. FIG. 6( c) is a top view of such a planar heatpipe. It should be understood that any of a variety of techniques can beused to join the cylindrical heat pipes 600 together to approximate theplanar heat pipe. For example, welding or soldering could be used. Also,a joining member 602 can be used to bundle the cylindrical heat pipes600 together, as shown in FIG. 6( d). FIG. 6( d) also depicts how oneend of the cylindrical heat pipes would engage with (and preferably bepositioned inside the heat exchanger 110.

Further still, other cross-sectional shapes can exist on the surface ofthe planar heat pipe if desired by a practitioner. For example, a seriesof rounded ridges 702 and troughs 704 may be positioned on the exposedsurface of the planar heat pipe 700 of FIG. 7. FIG. 7 shows across-sectional view of an exemplary planar heat pipe 500 with roundedridges and troughs. Similarly, more pointed ridges and troughs could beused as shown in FIG. 8( d) which reside on the upper surface 116 sheet(with vacuum space 800 residing between the upper sheet 116 and bottomsheet 118). These ridges and troughs could be beneficial for capturingsunlight when the sun is at lower elevations during the morning or earlyevening hours. As an additional example, a waffling or dimpling pattern802 can be applied to the exposed surface of the planar heat pipe 500 ofFIGS. 8( a) and (b). FIG. 8( a) shows a cross-sectional view of such anexemplary planar heat pipe 800, while FIG. 8( b) shows a top view. Anexample of an additional waffling pattern is shown in FIG. 8( c).Moreover, the upper and lower surfaces 116 and 118 of a heat pipe can bestamped together to leave a number of spaced half-cylinder vacuumchamber 800 as shown in FIG. 8( e). While the examples of FIGS. 8( c)and (d) show a small gap between the upper sheet 116 and lower sheet 118of the heat pipe, it should be understood that the upper and lowersheets 116 and 118 could be effectively made flush at the trough pointssuch that a gap only exists between the two sheets at the ridge portionsif desired.

FIG. 9( a) shows an exemplary embodiment for a manifold heat exchanger110. The main frame of FIG. 9( a) shows a bottom view of the exemplarymanifold heat exchanger 110 while the left frame shows a side view ofthe manifold heat exchanger 110 in FIG. 9( a). In this embodiment, theintake and outtake ports 114 a and 114 b extend out the bottom of theheat exchanger 110 at opposite lateral end portions of the heatexchanger 110. With reference to the embodiment shown in FIGS. 1(a)-(c), the heat exchanger embodiment of FIG. 9( a) has the ports 114 aand 114 b extending downward from the bottom of the heat exchanger 110rather than extending outward from the rear of the heat exchanger 110.The heat exchanger includes an internal reservoir chamber 900. An endportion 902 of the heat absorber 102 is also positioned inside thechamber 900. It should be noted that this end portion 902 may be possessa geometrical configuration or pattern that is designed to enhance heattransfer between the heat pipe 500 and the heat transfer fluid flowinginside the chamber 900.

Thus, as heat is absorbed by the heat absorber 102, heat will bedelivered to the heat absorber portion 902 inside the heat exchangerchamber 900. Then, as heat transfer fluid enters intake port 114 a itbecomes heated heat transfer fluid as it passes the heat source of theheat absorber portion 902. This heated heat transfer fluid then exitsthe chamber 900 via outtake port 114 b. FIG. 11( a), which is across-sectional side view along a short dimension of an exemplary heatexchanger 110 such as the one shown in FIG. 9( a), generally illustratesthis process.

FIG. 9( b) shows another exemplary embodiment for a manifold heatexchanger 110. The main frame of FIG. 9( b) shows a bottom view of thisexemplary manifold heat exchanger 110 while the left frame shows a sideview of the manifold heat exchanger 110 in FIG. 9( b). The embodiment ofFIG. 9( b) shows a dual chamber bidirectional flow manifold heatexchanger 110. With this embodiment, the reservoir chamber 900 comprisesan upper chamber 900 a separated from a lower chamber 900 b by adividing wall or the like. A plurality of intake ports 114 a 1 and 114 a2 and a plurality of outtake ports 114 b 1 and 114 b 2 are shown, withone intake/outtake port pair serving the upper chamber 900 a while theother intake/outtake port pair serves the lower chamber 900 b. In thisexample, the multiple intake ports and outtake ports are shown extendingfrom the bottom of the heat exchanger 110. However, this need not be thecase.

By having multiple chambers, the heat exchanger 110 can accommodatemultiple flows of heat transfer fluid, including flows of heat transferfluid in opposite directions. As such, the heat exchanger embodiment ofFIG. 9( b) can be referred to as a dual chamber bi-directional flow heatexchanger 110. FIG. 11( b) generally depicts how these bidirectionalfluid flows could be heated inside the chambers 902 a and 902 b for theheat exchanger 110 of FIG. 9( b). FIG. 11( c) generally depicts thebidirectional flow directions as well. Piping can deliver heat transferfluid flowing in one direction to the intake port 114 a 1 for the upperchamber 900 a while piping can deliver heat transfer fluid flowing inthe other direction to the intake port 114 a 2 opposite port 114 a 1.The heat transfer fluid would thus flow in opposite directions throughthe heat exchanger. This is shown in FIGS. 11( b) and (c) by fluid flow1102 through the upper chamber 900 a in a first direction and a fluidflow 1104 through the lower chamber 900 b in the opposite direction.This permits the return flow path of heat transfer fluid to a centralsource to stay within the insulating confines of the heat exchanger to agreater extent than having an exposed return path would provide. FIG.11( d) generally illustrates a bidirectional fluid flow through anexemplary array of solar collectors 100 a, 100 b and 100 c. In thisexample, fluid enters the array at point 1110, traverses the three solarcollectors through the upper flow paths 1102 and returns to the sourceat point 1112 through lower flow paths 1114. Short piping that passesthrough holes 310 in the solar collector sidewalls 122 can connectadjacent solar collectors, and a short U-connector pipe 1114 can be usedat the end point of the final solar collector 100 c in the array toreturn the fluid exiting the upper flow path 1102 of solar collector 100c to the lower flow path 1104 of solar collector 100 c.

It should be understood that a practitioner may choose to position theheat exchanger's ports 114 in any of a number of configurations. FIG.10( a) illustrates a top view of an exemplary heat exchanger 110 wherethe ports 114 extend laterally outward from the sides of the heatexchanger 110. FIG. 10( b) illustrates a side view of an exemplary heatexchanger 110 where one port (e.g., port 114 a) extends laterallyoutward from a side of the heat exchanger 110 while the other port(e.g., port 114 b) extends downward from the bottom of the heatexchanger 110. FIG. 10( c) illustrates a top view of an exemplary heatexchanger 110 where one port (e.g., port 114 a) extends laterallyoutward from a side of the heat exchanger 110 while the other port(e.g., port 114 b) extends out from the rear of the heat exchanger 110.However, it should be understood that still other configurations arepossible, particularly if multiple intake and outtake ports are used.Further still, it should be understood that the ports 114 can bepositioned as desired along the length, width and height of the heatexchanger 110, although it is preferred that the ports 114 be positionedto provide a flow path for the heat transfer fluid to absorb heat fromthe heat source of the heat absorber portion 902.

FIG. 13( a) depicts an embodiment where a plurality of the solarcollectors 100 disclosed herein are arranged in an array 1300. It shouldbe understood that number of solar collectors 100 to include in an arrayis up to a practitioner. To form the array, the solar collectors 100 arepreferably arranged together like puzzle pieces. With reference to theembodiment of FIGS. 3( a)-(f), piping 1302 for delivering heat transferfluid to and taking heat transfer fluid away from the heat exchangers110 can be positioned to pass through hole 310 and enter the open patharea 430, traverse the open path area 430 and exit the hole 312 on theopposite side of the solar collector. Such an arrangement would permitmultiple solar collectors 100 to positioned largely flush against eachother to maximize space usage. Similarly, by alternating male and femaleconnection ports between adjacent solar collectors, another largelyflush engagement could be achieved.

A trunk pipe line 1302 preferably connects different arrangements ofsolar collectors 100 in the array 1300. A plurality of branch pipe lines1320 and 1322 can sprout from each trunk line 1302 (preferablyperpendicularly). This is shown in FIG. 13( b). Branch line 1320provides heat transfer fluid to solar collectors 100 in a first flowdirection while heat transfer fluid flows through branch lines in theopposite direction. As such, it can be seen that the exemplaryembodiment of FIG. 13( b) is a suitable candidate for the dual chamberbidirectional flow heat exchanger 110 of FIG. 9( b). Thus, each branchline 1320/1322 has a plurality of serially connected solar collectorswhere the heated heat transfer fluid output of one solar collector isfed to the next solar collector down the line (including along thereturn path of line 1322). Trunk line 1302 preferably comprises a mainpipe 1310 where fluid flows in a first direction and a second main pipe1312 where fluid flows in the opposite direction. If desired, aU-connector piece can join the output of one end of pipe 1310 to theinput of the nearby end of pipe 1312. Alternatively, separate sourcesand terminations could be used at each end of pipes 1310 and 1312 ifdesired.

It should be understood that for each of illustration, the piping 1310and 1312 in FIGS. 13( a) and (b) is shown to reside outside thefootprint of the solar collectors 100. However, if desired, the piping1310 and 1312 can run through the frame sidewalls (see hole 310) viaopen path area 430 to reduce the amount of exposed piping and maximizespace usage. Further still, it should be understood that it is desirableto provide insulation around the pipes 1310 and 1312 so as to reduceheat loss.

FIG. 13( c) depicts another exemplary array embodiment wherein differentarrays 1300 are arranged in super-arrays 1350 that surround a centralcollection unit 1352. The central collection unit 1352 can serve as ajunction where a plurality of relatively lower pressure fluid pipelinesare joined in a relatively higher pressure fluid pipeline. If desired,the joined high pressure fluid flow can then be delivered via piping toa desired location from the central collection unit 1352. Alternatively,electrical generating components and/or energy consumption componentscan be placed at or near central collection unit 1352 to use the energyreceived from the solar collectors 100. In the example of FIG. 13( c),each central collection unit 1352 connects with 4 arrays 1300 as shownin FIG. 13( c) to form a super-array 1350.

To structurally gang solar collectors 100 together in an array 1300, astructural member 1360 (e.g., a steel bar) such as that shown in FIG.13( d) can be used. As shown in the top view of FIG. 13( d), a pluralityof solar collectors 100 can be attached to structural bars 1360 (e.g.,via bolts or the like connected to the solar collector sidewalls 122).These ganged solar collectors can then be put into place in the field asa single unit with a reduced number of crane operations to lift thesolar collectors and put them in position. Furthermore, the ganged solarcollectors are preferably pre-plumbed with the necessary piping andother connections so that only connections between pipe ends need to beperformed in the field. Each solar collector array preferably includesthe corresponding piping for lines 1310 and 1312, a vacuum pipe, and aconduit for low voltage electrical connections as discussed below.

An array 1300 can be positioned at a location where the solar collectorswill receive sufficient sunlight to produce a heated output for deliveryto downstream energy consumers. For example, arrays 1300 can be placedon the roof of large buildings such as shopping malls. As anotherexample, arrays 1300 can be placed at sunny locations in remote areassuch as deserts or beneath existing power lines. Furthermore, each solarcollector 100 can be supported by a tilting mechanism (see FIG. 14)having a plurality of columns 1400 that are configured to elevate ortilt the solar collector at a desired angle to increase the capture rateof solar energy. If desired, this tilting mechanism could includetracking capabilities (where the elevation of the array would beadjusted throughout the day to better catch sunlight) as is known in theart. For example, one common positioning technique is to deploy solarcollectors in a largely north/south orientation, tilt the solarcollectors to maximize sunlight capture and then adjust the solarcollector's angle and orientation to track the sunlight throughout theday.

FIGS. 15( a) and (b) depict exemplary techniques for maintaining vacuumpressure within the solar collector chambers 108 when a plurality ofsolar collectors 100 are combined in an array. The inventors believethat embodiments such as the ones described by FIGS. 15( a) and (b) willpermit more effective field maintenance of the vacuum pressure insidethe solar collector chambers. With reference to FIG. 15( a), a main pumpline 1500 is shown. This main line 1500 is preferably connected to avacuum pump that establishes a vacuum pressure. A plurality of branchpump lines 1502 can sprout off the main line 1500 as shown in FIG. 15(a). Each branch line 1502 connects to a plurality of solar collectors100 in an array. A solenoid valve 1504 can be positioned along a branchline 1502 upstream from a plurality of solar collectors connected tothat branch line 1502, as shown in FIG. 15( a). This solenoid valve 1504is configured with backflow prevention features as is known in the artto effectively provide isolation for the downstream solar collectors 100in case there is a fault elsewhere in the vacuum system. That is, shouldthere be a break somewhere along the main line 1500, the solenoid valve1504 will operate to protect the vacuum pressure inside the downstreamsolar collectors 100. Such operation could be achieved in any of anumber of ways. For example, the solenoid valves' default state aftervacuum pressure has been established can be in a closed state so as toprovide isolation by default between segmented solar collectors. Then,these solenoid valves can be actuated to an open state as needed shouldthere be a need to adjust the vacuum pressure in the affected solarcollectors. Alternatively, the solenoid valves' default state can be inan open state. Then, should the system detect a fault in vacuumpressure, select solenoid valves would be actuated to a closed state toachieve isolation of desired solar collectors.

One or more sensors 1506 for sensing the temperature and pressure inbranch line 1502 and/or fluid branch lines 1320/1322 can be employed todetect whether there are any problems in the vacuum system and whetherthe solar collectors are operating as desired. Based on the data sensedby sensors 1506 and processed by a controller (not shown), the solenoidvalves can be activated to open/close as desired. For example, toincrease the vacuum pressure in the downstream solar collectors, thecorresponding solenoid valve 1504 can be actuated (via a signal on a lowvoltage data/control line 1508) to the open position so that the vacuumpump can increase the vacuum pressure. It should also be understood thatthe sensors 1506 can be positioned in or on the solar collectors 100themselves to provide such data to a controller via data/control line1508 (e.g., as shown in connection with the FIG. 15( b) embodimentdiscussed below).

FIG. 15( b) depicts an exemplary embodiment where the vacuum isolationis provided on a solar collector-by-solar collector basis. With thisexemplary embodiment, the solenoid valve 1504 is used as the valve inthe tube valve 124 for connecting each solar collector to the branchpump line 1502. Control signals on line 1508 can then be used to operateeach individual solenoid valve as desired.

Furthermore, the inventors note while the exemplary solar collectorembodiments of FIGS. 1( a)-(c) and FIGS. 3( a)-(f) were configured suchthat the heat exchanger 110 was positioned at an end portion of thechamber 108 with reference to the long dimension of the solar collector,a solar collector 100 can also be arranged such that the heat exchanger110 is positioned at an end portion of the chamber 108 with reference tothe short dimension of the solar collector, as shown in FIG. 16, whichis a top view of such a solar collector arrangement.

Further still, the inventors note that the solar collector's bottommember 120 and sidewalls 122 can be encased in insulation 1700 tofurther protect the solar collector from heat loss to the outsideenvironment if desired by a practitioner (see FIGS. 17( a) and (b)).Varying thickness of insulation could be used by a practitionerdepending on the practitioner's desires (e.g., 18 inches). More, theinsulation should be able to accommodate the expected high temperaturesthat the solar collectors would exhibit when in use. Furthermore, apractitioner may choose to provide multiple layers of different types ofinsulation around the solar collectors. For example, the insulation mayinclude a first insulation layer contacting the frame that is capable ofwithstanding high temperatures and a second insulation layer around thefirst insulation layer that need not be configured to high temperatureduty (e.g., a foam-type insulation).

The inventors also note that, if desired by a practitioner, a pluralityof heat absorbers 102 (e.g., planar heat pipes 500) could be positionedin a single evacuated chamber, as shown in FIGS. 18( a)-(b). Embodimentssuch as these would permit larger solar collector length/widthdimensions and possibly result in a more efficient use of space withless material costs. The ports on the heat exchangers 110 can directlyconnect with each other inside the evacuated chamber 108, therebyeliminating any piping outside the chamber 108 that would otherwise beneeded to connect the heat exchangers for different heat absorbers 102.Also, it should be noted that the spacing between the various heatexchangers 110 is shown for ease of illustration. A practitioner maychoose to provide a more flush engagement of the different heatexchangers against each other so as to maximize the use of space insidethe chamber. Furthermore, it should be understood that a single heatexchanger 110 could be used to receive the end portions 902 of thedifferent heat absorbers 102 if desired. Further still, as shown in FIG.18( b), one or more structural members 1800 can be installed inside thechamber 108 to provide structural support for the solar collector'sframe (such support may be necessary given the increased dimensions thatcould arise in such embodiments. The example of FIG. 18( b) shows asupport beam member 1800 extending along the long dimension of the solarcollector inside the chamber 108 at around the mid-point of the chamber108 with respect to the short dimension. It should be understood thatsuch a beam 1800 could also be run along the short dimension at aroundthe mid-point of the chamber 108 with respect to the long dimension.Similarly, two support members 1800 could be run perpendicular to eachother along the long and short dimensions if desired. Such a supportmember 1800 need not seal off one portion of the chamber 108 fromanother—it need only provide structural support for the frame. Thechamber 108 in such an embodiment would be a single evacuated chamber.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of invention which is to be given the fullbreadth of the claims appended and any and all equivalents thereof. Itshould further be understood that the embodiments disclosed hereininclude any and all combinations of features as disclosed herein and/ordescribed in any of the dependent claims.

1. An apparatus for collecting solar energy, the apparatus comprising: aplanar heat pipe configured to absorb heat; a frame surrounding theplanar heat pipe, the frame forming a chamber within which at least aportion of the heat pipe resides; and a transparent cover engaged withthe frame to enclose the chamber; and wherein the chamber comprises anevacuated chamber.
 2. The apparatus of claim 1 wherein the entire heatpipe resides within the evacuated chamber, the apparatus furthercomprising: a heat exchanger in cooperation with the heat pipe, the heatexchanger comprising a heat exchanger chamber and an output, the heatexchanger being configured to receive and transfer the heat absorbed bythe heat pipe to the output, wherein the heat exchanger chamber ispositioned inside the evacuated chamber.
 3. The apparatus of claim 2wherein the heat exchanger further comprises a heat transfer fluid forentering the heat exchanger chamber to absorb heat from the heat pipeand transporting the absorbed heat to the output.
 4. The apparatus ofclaim 2 wherein the heat exchanger chamber comprises a first heatexchanger chamber and a second first heat exchanger chamber.
 5. Theapparatus of claim 5 wherein the heat exchanger comprises amulti-chamber bidirectional flow manifold heat exchanger.
 6. Theapparatus of claim 2 wherein the frame comprises a bottom member and aplurality of sidewalls, the apparatus further comprising a reflectorpositioned and configured to reflect energy radiated by the heat pipeback to the heat pipe.
 7. The apparatus of claim 6 wherein the reflectoris positioned inside the chamber.
 8. The apparatus of claim 7 whereinthe reflector comprises a reflector positioned between the heat pipe andthe bottom wall.
 9. The apparatus of claim 8 wherein the reflectorcomprises a mirror.
 10. The apparatus of claim 9 wherein the mirrorcomprises a coating, the coating configured to reflect infrared energy.11. The apparatus of claim 6 wherein the heat pipe does not contact theframe.
 12. The apparatus of claim 2 further comprising a plurality ofthe planar heat pipes positioned inside the evacuated chamber.
 13. Theapparatus of claim 1 wherein the heat pipe comprises a plurality ofholes, wherein the frame comprises a bottom member, the apparatusfurther comprising: a plurality of free-floating pins positioned tosupport the heat pipe without the heat pipe contacting the frame, thepins having a bottom portion for engaging the bottom member and a topportion for engaging the transparent cover, and wherein the pins passthrough the heat pipe holes.
 14. The apparatus of claim 13 wherein thepins further comprise a shoulder portion upon which the heat pipe issupported.
 15. The apparatus of claim 14 wherein the pins are formedfrom a material that is substantially non-heat-conducting.
 16. Theapparatus of claim 14 wherein the pins comprise ceramic pins.
 17. Theapparatus of claim 1 further comprising a tube valve passing through theframe for connection to a vacuum pump line, the vacuum pump line havinga solenoid valve connected thereto, the solenoid valve connecting thevacuum pump line to another vacuum pump line, the solenoid valveconfigured to maintain a vacuum pressure inside the chamber and isolatethe chamber from the another vacuum pump line in response to a solenoidvalve control signal.
 18. The apparatus of claim 1 further comprising atube valve passing through the frame for connection to a vacuum pumpline, the tube valve comprising a solenoid valve for connecting thechamber to a vacuum pump line, the solenoid valve configured to maintaina vacuum pressure inside the chamber and isolate the chamber from thevacuum pump line in response to a solenoid valve control signal.
 19. Theapparatus of claim 1 wherein the frame has a rectangular shape.
 20. Theapparatus of claim 19 wherein the transparent cover has a surface areaportion through which light enters the chamber, and wherein the heatpipe has a surface area that takes up around 95% of the transparentcover surface area portion.
 21. The apparatus of claim 1 furthercomprising a sealant layer between the frame and the transparent coverfor creating a seal between the transparent cover and the frame.
 22. Theapparatus of claim 1 wherein the planar heat pipe comprises a pluralityof cylindrical heat pipes that are arranged to approximate a flat plate.23. The apparatus of claim 1 wherein the planar heat pipe has aplurality of ridges and troughs on an upper surface thereof.
 24. Amethod for collecting solar energy, the method comprising: absorbingheat with a solar collector, the solar collector comprising a planarheat pipe positioned inside an evacuated chamber formed by a frame and atransparent cover.
 25. The method of claim 24 wherein the heat absorbingstep comprises absorbing the heat with the heat pipe, the method furthercomprising: transferring the absorbed heat to a heat exchanger, the heatexchanger having a heat exchanger chamber, the heat exchanger chamberalso positioned inside the evacuated chamber.
 26. The method of claim 25further comprising: heating a heat transfer fluid inside the heatexchanger chamber with the transferred heat; and transporting the heatedheat transfer fluid out of the heat exchanger chamber.
 27. The method ofclaim 25 wherein the heat exchanger chamber comprises a first heatexchanger chamber and a second first heat exchanger chamber.
 28. Themethod of claim 27 further comprising providing a bidirectional flow ofheat transfer fluid through the first and second heat exchangerchambers.
 29. The method of claim 25 further comprising: reflectingenergy radiated by the heat pipe back to the heat pipe with a reflector.30. The method of claim 29 wherein the reflector is positioned insidethe evacuated chamber.
 31. The method of claim 30 wherein the reflectoris positioned between the heat pipe and a bottom member of the frame.32. The method of claim 31 wherein the reflector comprises a mirror. 33.The method of claim 32 wherein the mirror comprises a coating, thecoating configured to reflect infrared energy.
 34. The method of claim25 wherein the heat pipe does not contact the frame.
 35. The method ofclaim 24 wherein the heat pipe comprises a plurality of holes, themethod further comprising: supporting the heat pipe within the framewith a plurality of free-floating pins that pass through the heat pipeholes, the pins positioned to support the heat pipe without the heatpipe contacting the frame, the pins having a bottom portion for engaginga bottom member of the frame and a top portion for engaging thetransparent cover.
 36. The method of claim 35 wherein the pins furthercomprise a shoulder portion upon which the heat pipe is supported. 37.The method of claim 36 wherein the pins are formed from a material thatis substantially non-heat-conducting.
 38. The method of claim 36 whereinthe pins comprise ceramic pins.
 39. The method of claim 24 wherein thesolar collector comprises a tube valve passing through the frame, themethod comprising: connecting the tube valve to a vacuum pump line, thevacuum pump line having a solenoid valve connected thereto, the solenoidvalve connecting the vacuum pump line to another vacuum pump line; andcontrolling the solenoid valve to maintain a vacuum pressure inside thechamber and isolate the chamber from the another vacuum pump line in theevent of a fault along the another vacuum pump line.
 40. The method ofclaim 24 wherein the solar collector comprises a tube valve passingthrough the frame, the tube valve comprising a solenoid valve, themethod comprising: connecting the tube valve to a vacuum pump line; andcontrolling the solenoid valve to maintain a vacuum pressure inside thechamber and isolate the chamber from the vacuum pump line in the eventof a fault along the vacuum pump line.
 41. The method of claim 24wherein the frame has a rectangular shape.
 42. The method of claim 41wherein the transparent cover has a surface area portion through whichlight enters the chamber, and wherein the heat pipe has a surface areathat takes up around 95% of the transparent cover surface area portion.43. The method of claim 24 further comprising: creating a seal betweenthe transparent cover and the frame with a sealant layer.
 44. The methodof claim 24 wherein a plurality of the planar heat pipes are positionedinside the evacuated chamber.
 45. An apparatus for collecting solarenergy, the apparatus comprising: a planar heat pipe configured toabsorb heat, the heat pipe having a plurality of holes; a frame, theframe comprising a bottom member and a plurality of sidewalls forming achamber within which the heat pipe resides; a transparent cover engagedwith the frame to enclose and seal the chamber, wherein the chambercomprises an evacuated chamber; a heat exchanger in cooperation with theheat pipe, the heat exchanger comprising a heat exchanger chamber and anoutput, the heat exchanger being configured to receive and transfer theheat absorbed by the heat pipe to the output, wherein the heat exchangerchamber is positioned inside the evacuated chamber; and a plurality offree-floating pins positioned to support the heat pipe without the heatpipe contacting the frame, the pins having a bottom portion for engagingthe bottom member and a top portion for engaging the transparent cover,and wherein the pins pass through the heat pipe holes.
 46. An apparatusfor collecting solar energy, the apparatus comprising: a heat absorberconfigured to absorb heat; a frame adapted to form a chamber withinwhich at least a portion of the heat absorber resides; a transparentcover engaged with the frame to enclose the chamber, the coverconfigured to permit solar energy to enter the chamber and impact theheat absorber; and a reflector positioned and configured to reflectenergy radiated by the heat absorber back to the heat absorber.
 47. Theapparatus of claim 46 wherein the reflector is positioned inside thechamber.
 48. The apparatus of claim 47 wherein the frame comprises abottom member and a plurality of sidewalls, and wherein the reflector ispositioned between the heat absorber and the bottom wall.
 49. Theapparatus of claim 48 wherein the reflector comprises a mirror.
 50. Theapparatus of claim 48 wherein the reflector comprises a coating, thecoating configured to reflect infrared energy.
 51. The apparatus ofclaim 50 wherein the coating comprises a coating applied to a surfacebelow the heat absorber.
 52. The apparatus of claim 50 wherein the heatabsorber has a bottom surface, and wherein the coating comprises acoating applied to the heat absorber bottom surface.
 53. The apparatusof claim 47 wherein the frame comprises a bottom member and a pluralityof sidewalls, and wherein the reflector is positioned on an internalface of at least one of the sidewalls.
 54. The apparatus of claim 48further comprising a coating applied to an underside of the transparentcover, the coating configured to pass energy from outside the apparatusinto the chamber and also configured to reflect energy radiated by theheat absorber back to the heat absorber.
 55. The apparatus of claim 46further comprising: a heat exchanger in cooperation with the heatabsorber, the heat exchanger configured to receive and transfer the heatabsorbed by the heat absorber to an output.
 56. The apparatus of claim55 wherein the heat absorber comprises a planar heat pipe.
 57. Theapparatus of claim 56 wherein the planar heat pipe comprises a flatplate heat pipe.
 58. The apparatus of claim 55 wherein the chambercomprises an evacuated chamber.
 59. A method comprising: within a solarcollector having a heat absorber positioned inside a chamber, reflectingenergy radiated by the heat absorber back to the heat absorber with areflector.
 60. The method of claim 59 wherein the reflector ispositioned inside the chamber.
 61. The method of claim 60 wherein thesolar collector comprises a bottom member, a plurality of side walls anda transparent cover for defining the chamber, and wherein the reflectoris positioned between the heat absorber and the bottom member.
 62. Themethod of claim 61 wherein the reflector comprises a mirror.
 63. Themethod of claim 61 wherein the reflector comprises a coating, thecoating configured to reflect infrared energy.
 64. The method of claim63 wherein the heat absorber comprises a planar heat pipe.
 65. Themethod of claim 61 wherein the chamber comprises an evacuated chamber.66. The method of claim 60 wherein the reflector is positioned on aninternal face of at least one of the sidewalls.
 67. The method of claim60 wherein the reflector comprises a coating applied to an underside ofthe transparent cover, the coating configured to pass energy fromoutside the apparatus into the chamber and also configured to reflectenergy radiated by the heat absorber back to the heat absorber.
 68. Amethod comprising: within a solar collector having a heat absorberpositioned inside a chamber, the chamber being formed by a bottommember, a plurality of side walls and a transparent cover, positioningan energy reflector between the heat absorber and the bottom member. 69.The method of claim 68 further comprising: reflecting energy radiated bythe heat absorber back to the heat absorber with the energy reflector.70. The method of claim 68 wherein the energy reflector comprises amirror.
 71. The method of claim 68 wherein the energy reflectorcomprises a coating, the coating configured to reflect infrared energy.72. An apparatus comprising: a flat plate solar collector having anevacuated chamber within which a heat absorber and a reflector arepositioned, the reflector being positioned beneath the heat absorber forreflecting energy radiated by the heat absorber back to the heatabsorber.
 73. The apparatus of claim 72 wherein the reflector comprisesa mirror, the mirror having a coating, the coating configured to reflectinfrared energy.
 74. An apparatus for collecting solar energy, theapparatus comprising: a heat absorber configured to absorb heat; a framesurrounding the heat absorber, the frame forming a chamber within whichthe heat absorber resides; a transparent cover engaged with the frame toenclose and seal the chamber, wherein the chamber comprises an evacuatedchamber; and a heat exchanger in cooperation with the heat absorber, theheat exchanger comprising a heat exchanger chamber and an output, theheat exchanger being configured to receive and transfer the heatabsorbed by the heat absorber to the output, wherein the heat exchangerchamber is positioned inside the evacuated chamber.
 75. The apparatus ofclaim 74 wherein the heat exchanger chamber comprises a heat transferfluid for absorbing heat from the heat absorber and transporting theabsorbed heat to the output.
 76. The apparatus of claim 75 wherein theheat exchanger chamber comprises a first chamber and a second chamber,the first and second chamber configured to separately heat differentflows of heat transfer fluid.
 77. The apparatus of claim 76 wherein theheat exchanger chambers are configured to receive a bidirectional flowof heat transfer fluid in the first and second chambers.
 78. Theapparatus of claim 74 wherein the heat exchanger chamber does notcontact the frame.
 79. The apparatus of claim 78 comprises a standoffsleeve positioned to connect the heat exchanger chamber to the frame,the standoff sleeve comprising a material that is resistant to heatconduction.
 80. The apparatus of claim 79 wherein the standoff sleevematerial comprises a ceramic.
 81. A method for collecting solar energy,the method comprising: absorbing heat with a heat absorber, wherein theheat absorber is positioned inside an evacuated chamber formed by aframe and a transparent cover of a solar collector; and transferring theabsorbed heat to a heat exchanger, the heat exchanger comprising a heatexchanger chamber, wherein the heat exchanger chamber is also positionedinside the evacuated chamber.
 82. The method of claim 81 furthercomprising: heating a heat transfer fluid inside the heat exchangerchamber with the transferred heat; and transporting the heated heattransfer fluid out of the heat exchanger chamber.
 83. The method ofclaim 82 wherein the heat exchanger chamber comprises a first chamberand a second chamber, the method further comprising separately heatingdifferent flows of heat transfer fluid within the first and secondchambers.
 84. The method of claim 83 wherein the flows comprisebidirectional flows of heat transfer fluid.
 85. The method of claim 81wherein the heat exchanger chamber does not contact the frame.
 86. Themethod of claim 85 further comprising insulating the heat exchangerchamber with a standoff sleeve positioned to connect the heat exchangerchamber to the frame, the standoff sleeve comprising a material that isresistant to heat conduction.
 87. The method of claim 86 wherein thestandoff sleeve material comprises a ceramic.
 88. An apparatus forcollecting solar energy, the apparatus comprising: a heat absorberconfigured to absorb heat, the heat absorber comprising a plurality ofholes; a frame, the frame comprising a bottom member and a plurality ofsidewalls that form a chamber within which the heat absorber resides; atransparent cover engaged with the frame to enclose and seal thechamber, wherein the chamber comprises an evacuated chamber; and aplurality of free-floating pins positioned to support the heat absorberwithout the heat absorber contacting the frame, the pins having a bottomportion for engaging the bottom member and a top portion for engagingthe transparent cover, and wherein the pins pass through the heatabsorber holes.
 89. The apparatus of claim 88 wherein the pins furthercomprise a shoulder portion upon which the heat absorber is supported.90. The apparatus of claim 89 wherein the pins are formed from amaterial that is substantially non-heat-conducting.
 91. The apparatus ofclaim 89 wherein the pins comprise ceramic pins.
 92. The apparatus ofclaim 88 further comprising a cushion layer disposed on at least one ofthe ends of the pins.
 93. A method for collecting solar energy, themethod comprising: absorbing heat with a heat absorber wherein the heatabsorber is positioned inside an evacuated chamber formed by a frame anda transparent cover of a solar collector, the heat absorber comprising aplurality of holes; and supporting the heat absorber within the framewith a plurality of free-floating pins that pass through the heatabsorber holes, the pins positioned to support the heat absorber withoutthe heat absorber contacting the frame, the pins having a bottom portionfor engaging a bottom member of the frame and a top portion for engagingthe transparent cover.
 94. The method of claim 93 wherein the pinsfurther comprise a shoulder portion upon which the heat pipe issupported.
 95. The method of claim 94 wherein the pins are formed from amaterial that is substantially non-heat-conducting.
 96. The method ofclaim 94 wherein the pins comprise ceramic pins.
 97. The method of claim93 further comprising cushioning an engagement between the pins and atleast one of the bottom member and the transparent cover with a cushionlayer disposed on at least one of the ends of the pins.
 98. An apparatusfor collecting solar energy, the apparatus comprising: a vacuum pumpline for connection to a vacuum pump; a plurality of branch vacuum pumplines for connection to the vacuum pump line; a plurality of solarcollectors connected to at least one of the branch vacuum pump lines toform an array of solar collectors, each solar collector comprising anevacuated chamber, a heat absorber positioned at least partially insidethe chamber, and a tube valve for connection to the at least one branchvacuum pump line; and a solenoid valve connecting the vacuum pump linewith the at least one branch vacuum pump line, the solenoid valve beingconfigured to open and close to maintain a vacuum pressure inside thechambers of the solar collectors in the array and isolate the solarcollectors in the array from the vacuum pump line in response to acontrol signal.
 99. A method for collecting solar energy, the methodcomprising: collecting energy with a plurality of solar collectors, eachsolar collector comprising an evacuated chamber and a heat absorberpositioned inside the evacuated chamber; and using at least one solenoidvalve to maintain a vacuum pressure inside the evacuated chambers andisolated the evacuated chambers from an upstream vacuum pressure fault.100. The method of claim 99 wherein the solenoid valve using stepcomprises using a solenoid valve that connects a branch vacuum pump lineto a vacuum pump line, wherein the solar collectors are connected to thebranch vacuum pump line to create a vacuum pressure inside the chambers.101. The method of claim 99 wherein the solenoid valve using stepcomprises using the solenoid valve to directly connect the solarcollectors to a vacuum pump line.
 102. An apparatus for collecting solarenergy, the apparatus comprising: a plurality of branch pipe lines; atrunk pipe line configured to deliver heat transfer fluid to theplurality of branch pipe lines; and a plurality of solar collectorsserially connected to at least one of the branch pipe lines to form anarray of solar collectors.
 103. The apparatus of claim 102 wherein eachsolar collector comprises a multi-chamber bidirectional manifold heatexchanger that is configured to receive a flows of heat transfer fluidin a first direction and a second direction.
 104. The apparatus of claim102 wherein the plurality of solar collectors formed in the array arejoined together by a structural member.
 105. The apparatus of claim 102wherein a plurality of the arrays are formed into a super-array around acentral collection unit.
 106. The apparatus of claim 102 wherein eachsolar collector in the array comprises an open path area on an undersidethereof for receiving piping to serially connect the solar collectors inthe array.
 107. The apparatus of claim 102 wherein each solar collectorcomprises: (1) a planar heat pipe configured to absorb heat, (2) a framesurrounding the planar heat pipe, the frame forming a chamber withinwhich at least a portion of the heat pipe resides, and (3) a transparentcover engaged with the frame to enclose the chamber, wherein the chambercomprises an evacuated chamber.
 108. A method comprising: deliveringheat transfer fluid from a trunk pipe line to a plurality of branch pipelines, wherein at least one of the branch pipe lines comprises aplurality of solar collectors serially connected to form an array ofsolar collectors; and collecting energy with the array of solarcollectors to heat the delivered heat transfer fluid.
 109. The method ofclaim 108 wherein each solar collector comprises a multi-chamberbidirectional manifold heat exchanger, the method further comprisingeach solar collector in the array receiving flows of heat transfer fluidin a first direction and a second direction.
 110. The method of claim108 further comprising joining the solar collectors in an array togetherwith a structural member.
 111. The method of claim 108 furthercomprising forming a plurality of the arrays into a super-array around acentral collection unit.
 112. The method of claim 108 wherein each solarcollector in the array comprises an open path area on an undersidethereof for receiving piping to serially connect the solar collectors inthe array.
 113. The method of claim 108 wherein each solar collectorcomprises: (1) a planar heat pipe configured to absorb heat, (2) a framesurrounding the planar heat pipe, the frame forming a chamber withinwhich at least a portion of the heat pipe resides, and (3) a transparentcover engaged with the frame to enclose the chamber, wherein the chambercomprises an evacuated chamber.